Conventional dc electromagnetic motors are energized by application of electrical current to stator coils, which creates a magnetic field that forces an armature to move from a rest position. When the current to the primary coils of the electromagnetic motor is terminated, a collapsing magnetic field is momentarily created. Where it is desired to return the armature to its original position after the electric current is terminated, a mechanical spring may be utilized for such a purpose. In any event, energy of the collapsing field is essentially wasted.
It is an object of this invention to provide an electromagnetic motor that employs the collapsing field caused by termination of stator coil current to move the armature to another position. It is a further object to provide electromagnetic motors that are of relatively simple and economical design, manufacture and assembly.
An electromagnetic motor in accordance with preferred embodiments of the present invention includes a stator assembly having a stator body with at least one pole, a primary coil associated with the stator body and electrically interconnected with a power supply such that electric current in the primary coil creates a magnetic field in the pole, a secondary coil associated with the stator body and magnetically coupled with the body and primary coil, and a permanent magnet armature positioned so that there is a working air gap between the armature and the pole. In accordance with one important aspect of the invention, termination of current flow to the primary coil results in a collapsing magnetic field that induces an electric current in the secondary coil to reverse the magnetic polarity at the stator pole, and thereby reverse magnetic attractive/propulsion force on the armature. An important advantage is that the armature is positively moved by magnetic forces when current is terminated in the primary coil, resulting in a more efficient motor while reducing or eliminating any need for a return spring.
The stator assembly in one embodiment of the invention comprises first and second stator bodies that are in spaced mirror symmetrical relationship. The first stator body has a pair of poles aligned with a pair of poles of the second stator body, and first and second primary coils are respectively disposed on the stator bodies. First and second secondary coils are respectively disposed on the stator bodies and electromagnetically coupled to the associated stator bodies and primary coils, and a rectifier is electrically connected to each secondary coil. When the electric current is terminated to the primary coils, a consequent collapsing magnetic field induces an electric current in the secondary coils, and this current is directed by the rectifier to reverse the polarities on the stator poles, which results in moving the armature to another position. This reduces the energy needed to move the armature to the opposite position.
The stator assembly in a second embodiment of the invention includes an annular stator body having four orthogonally spaced poles. Four primary coils are disposed around respective poles, and four secondary coils are disposed around respective poles and electromagnetically coupled to the stator body and the associated primary coils. Each secondary coil is connected to a rectifier to direct the induced electric current in a direction to reverse the polarity in the pole on which the secondary coil is disposed. In this second embodiment, when the current is terminated to a primary coil, the consequent collapsing magnetic field induces an current in the associated secondary coil that reverses the polarity in the respective pole and provides added energy to assist in moving the armature.
Other objects and features of the invention will become apparent in the following description and claims, in which the invention is described together with details to enable persons skilled in the art to practice the same, all in connection with the best modes presently contemplated for practicing the invention.